مطالعه موردی بارش منطقه تهران متأثر از آلودگی ذره ای

The relationship between precipitation and particle pollutants in Tehran as metropolitan city has been investigated. This study plays an important role for meteorologists and environmental researchers. The influence of particle pollutant on precipitation process in various regions of Tehran including Northeast (Aghdasie), Northwest (Geophysic), East (Sorkhe hesar), West (Mehr Abad) and the center (Bazar) has been studied .These investigations has been proceed in two ways: desirable days (particle pollutant less than ١٠٠ μg/m٣ ) and undesirable days (particle pollutant more than ٢٠٠ μg/m٣ ) in warm and cold seasons in a period of ٥ years (١٩٩٩ – ٢٠٠٣ ). The analysis of isohypse /particle pollutant isograms in undesirable conditions for each precipitation event show that in both warm and cold seasons, the amount of precipitation during the day increases from downtown toward the north of city, due to decrease of particle pollutants concentration. The averages of precipitation in Northern stations are higher than central, Western and Eastern stations due to their higher elevations. these averages in undesirable days decreases from Westside to East and increase in desirable days. The precipitation trends increases for all stations in desirable conditions in warm and cold seasons and decreases in undesirable conditions. Study of all data in desirable and undesirable days in cold and warm seasons shows that, in desirable condition the precipitation trends increase, probably due to inadvertent cloud seeding. In undesirable condition due to increase of particle pollutants as cloud condensation nuclei (CCN), the precipitation trends decrease probably due to cloud over seeding. Majority of stations in warm season shows that the maximum value of precipitation in desirable and undesirable days are a bit more than its value at clod season , mainly due to higher thickness of clouds and more precipitation intensity in warm season

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